local modem = peripheral.find("modem")
local speaker = require("speaker-driver")
local SERVER_PORT = 100
local CLIENT_PORT = 101

local username = os.getComputerLabel() or ("User" .. os.getComputerID())

local function start()
    if modem then
        modem.open(CLIENT_PORT)
        modem.transmit(SERVER_PORT, CLIENT_PORT, { type = "join", username = username })
    end
    print("Chat program started as " .. username)
end

local function stop()
    if modem then
        modem.transmit(SERVER_PORT, CLIENT_PORT, { type = "leave", username = username })
        modem.close(CLIENT_PORT)
    end
    print("Chat program stopped.")
end

local function restart()
    stop()
    start()
end

local function receiveLoop()
    while true do
        local event, side, channel, replyChannel, message, distance = os.pullEvent("modem_message")
        if channel == CLIENT_PORT and type(message) == "table" then
            local x, y = term.getCursorPos()
            term.setCursorPos(1, y)
            term.clearLine()
            
            if message.type == "system" then
                print("[System] " .. message.content)
                speaker.play("notification")
            elseif message.type == "chat" then
                print(message.username .. ": " .. message.content)
                speaker.play("notification")
            end
            
            write("> ")
        end
    end
end

local function sendLoop()
    while true do
        write("> ")
        local input = read()
        if modem then
            modem.transmit(SERVER_PORT, CLIENT_PORT, { type = "chat", username = username, content = input })
        end
    end
end

local function main()
    if not modem then
        print("No modem attached")
        while true do os.pullEvent() end
    end
    
    parallel.waitForAny(receiveLoop, sendLoop)
end

return { start = start, stop = stop, restart = restart, main = main }